Change severity of template instantiation message [backport] (#14526)

* Change severity of template instatiation msg

* Add a test

* Trailing newline argh

(cherry picked from commit 3698f19)

compiler/msgs.nim

@@ -380,7 +380,7 @@ proc writeContext(conf: ConfigRef; lastinfo: TLineInfo) =
     if context.info != lastinfo and context.info != info:
       if conf.structuredErrorHook != nil:
         conf.structuredErrorHook(conf, context.info, instantiationFrom,
-                                 Severity.Error)
+                                 Severity.Hint)
       else:
         let message = if context.detail == "":
           instantiationFrom

nimsuggest/tests/ttempl_inst.nim

@@ -0,0 +1,13 @@
+template foo() =
+  {.warning: "foo".}
+
+foo()
+
+#[!]#
+discard """
+$nimsuggest --tester $file
+>chk $1
+chk;;skUnknown;;;;Hint;;???;;0;;-1;;"ttempl_inst [Processing]";;0
+chk;;skUnknown;;;;Hint;;$file;;4;;3;;"template/generic instantiation from here";;0
+chk;;skUnknown;;;;Warning;;$file;;2;;11;;"foo [User]";;0
+"""